The AeropIane. By Claude Grahame-White and Harry Harper. Philadelphia: J. B. Lippincott Company, 1911. 317 pp.; 93 illustrations. Price, $3.50. Although the title of this book reads “Th0 Aeroplane, Past, Present and Future, by Claude Grahame-White and Harry Harper,” only a few articles are to be credited either to Mr. Grahame-White or to Mr. Harper. Just why they should figure as authors, seems somewhat mysterious. As a popular book on aeroplanes, the book is likely to serve a useful purpose, even though there are probably now no less than three or four dozen simply-worded volumes on aeroplanes struggling for existence In the book mark"t. Much practical information is not conveyed. By far the best article in the book is Col. J. H. Capper's discussion of the aeroplane in warfare, a sane presentation of the possibilities and limitations of the tying machine for military purposes. For popular reading, the book can be commended; but for valuable technical information, the reader will find it far too ephemeral. Die ExperimEntelle Grundlegung deR Atomistik. Von Werner Mecklenburg. Jena: Gustav Fischer, 1910. 140 pp. Price, 250 marks. The atomic hypothesis has long possessed a double sphere of usefulness. To the chemist it has represented a most convenient picture by means of which to express in simple terms, the “laws of chemIcal combination.” So convenient, indeed, to the chemist, has been the language of the atomic theory, and so generally adopted has its use become, that when Wald pointed out, some years ago, how all the facts ' of Etoichiometry could be accounted for without recourse to this hypothesis, he found himself speaking to a rather unappreciative audience, and would probably have passed almost unnoticed but for the authoritative support lent to him by Ost· wald in his Faraday lecture and on other occasions. ''here seems to be little douat now that the evidence of chemistry alone would have been insufficient to firmly establish the atomic hypothesis. But, on the other hand, this hypothesis has been of supreme interest to the physicist, firstly, in its relation to the mechanical theory of heat, with its off-shoot, the kiRetic theory of gases, of solutions, and latterly, also of suspensions ; and secondly, in the de velopmen t o' the electron theory. The evidence which has thus accumulated in favor of the atomic hypothesis is now well nigh irresistibly convincing, so that even Ostwald, formerly so strongly opposed to the atomistic point of view, openly declares himself its adherent, and definitely accepts the atomic constitution of matter as one of the basic starting points of chemical science, in his last edition of his “Outlines of General Chemistry.” The author of the book under review may be envied for the extremely grateful task which he has undertaken"-'that or laying before the reader a concise and yet essentially complete account of a field of physical science,. which has from the first possessed features of remarkable interest, but which especially in later years, has brought developments nothing short of spectacular. Have we not today direct optical evidence 9f particles very little greater in size than the calculated dimensions of an elementary molecule? Particles which, be it said, display all the characteristic properties and phenomena foreseen by the theoretical phYSicist in his investigations of the nature and behavior of molecules. If the determination on theoretical grounds of the molecular dimensions by the work of Clau-sius, Maxwell, Boltzmann, impresses us as a trlumph!l ieat of human intellect, the confirmation of their conclusions by direct experiment comes as a crowning testimony, both to the power of that intellect, and to the resources of experimental skill. And if the subject is one of remarkable interest, the author has been equally fortunate in his treatment of it. In the course of four chapters, he lays before the reader in simple terms the main experimental facts and theoretical lines of reasoning upon which the modern structure of the atomic hypothesiS Is built. The trst chapter Is headed “The Existence of Discrete Particles In Seemingly Homogenous Solutions ;” the second deals with “'l'he Dimensions of the Molecules as Determined by the Kinetic Tleory oi Gases.” The third chapter is devoted to that remarkable phenomena, known for some time, but almost forgotten by the physicist, the Brownian movement, which has quite recently proved suc9 a rich mine of information of the highest importance in the final establishment of the atomic theory upon an experimental basis. The fourth and last chapter deals with another subject the study of which has proved one of the most fertile fields of modern physical research, and has contributed among other things, the very cornerstone of the atomistic poInt of view. 'l'he author has succeeded In striking a most happy medium between a purely popular presentation on the one hand. which, for lack of detail, would fail to give the reader a true insight Into the nature of the very renarkable .evelopments discussed, and, on the other hand, a highly technical treatise, from which only the specialist could derive any advantage. 'rhe book is most hlg1y recommended to all whn take nn interest in the chemkal and physical phenomena to which it refers, and quite especially to those who, having at least some knowledge of the subject, wish to refresh their memories on familiar points, and to bring their acquaintance with a most fascinating province of physics up to date. It is heartily to be wished that translations of this work into English and French may soon appear upon the book market. A few such errors as unavoidably occur in a first edition have been noted in perusing the book, and may be listed here for th” benefit of the reader. On page 22, line six from below, the symbol x has apparently been omitted after the word “Hohe.” This might possibly cause some confusion. On page 25, it is stated that a table of molecular dimenGions, etc., is appended at the end of the book. In point of fact, this table appears between pages 64 and 65. On page 106, the word “Grammolekiilen” should evidently be “Gasmolekiilen.” These trilling errors do not, of course, in any way detract from the very high value of the book before us. Power. By Charles E. Lucke, Ph.D. New York: The Columbia University Press, 1911. 316 pp. Price, $2 net. In 1910 Prof. Lucke delivered a series of eight lectures on the phases of power. These lectures have now been incorporated in book form in a worthy manner. The titles of the lectures are the following: I. The Relation of Mechanical Power and Machinery to Social Conditions; II. Means Employed for the Substitution of Power for the Labor of Men; III. Essential Elements of Steam-Power Systems; IV. Principles of Efficiency in Steam-Power Systems; V. Processes and Mechanism of thp Gas-Power System; VI. Adaptation of Fuels for the Use of Internal Combustion Engines: VII. Water-Power Systems and Basal Hydraulic Processes ; VIII. Social and Economic Consequences of the Substitution of Power for Hand Labor. The lectures are all of them written with such clearness that a layman of Intelligence ought to be able to understand them. A Pottery Primer. By W. P. Jervis. New York: The O'Gorman Publishing Company, 1911. 8vo.; 188 pp.; illustrated. Price, $1. It is not surprising that the art and craft of pottery should appeal strongly to the artistic bent of mind, or that Its products should have raised up an enthusiastic army of collectors. Its history appeals to us on many sides. It has associations which bind past and present, foreign and native. It builds up common clay into expressions-often very beautiful expressions-of the higher mind. It is tower-like in its fragility, in its blending of body and spirit. Its symbolism has permeated the literature of the world for countless ages. In “A Pottery Primer” is conveyed to us this dual presentment of body and mind-the tel"minology, processes and technique of the craft, together with not a little of the grace and eternal freshness that clings to the art. The illustrations place before us examples of ancient treasures and more modern works, and admirably serve the writer's avowed purpose to awaken the reader to a desire for further research. In addition to the plates, cups, and vases which typify succeeding phases of history, we have gUmpses of panels, lanterns, fountains, and mantels of distinction. This is really much more than a mere primer, and is a noteworthy addition to Mr. Jervis's earlier works on ceramics, pottery, and pottery marks. RADIUMNORMALMASSE UND DEREN VERWEN-DUNG REI RADIOAKrIVEN MESSUNGEN. By E. Rutherford. Leipzig: Akademische Verlagsgesellschaft m. b. H., 1911. In the course of the last decade our knowledge of radioactivity has rapidly widened. Not only have the types of radioactive substances which emit radiations been carefully studied, but much labor has been spent in trying to fathom the nature of the complicated processes which occur in radioactive matter. A theory has been proposed which for the time being, explains satisfactorily a great number of phenomena. That theory, which is called the transformation or disintegration theory, was trst proposed by Rutherford and Soddy in 1903, and was based upon the supposition that the radioactive atom is unstable, and that it decomposes with explosive violence, at the same time emitting characteristic radiations. As the result of this atomistic explosion, a new atom is produced, quite different from the parent in chemical and physical proportions. These new atoms are also unstable, and give rise to another set of atoms. Thus the process may continue for some time. In investigations of this kind standards of some kind are necessary. This book of Prof. Rutherford's, which is no doubt familiar to many English readers in its original English expresses the necessity for a normal mass of radium and its use in radioactive measurements, a matter which was discussed at the last radiological congress held In September, 191 (, in Brussels. A Year in a CoaIrMine. By Joseph Husband. Boston: Houghton Mifflln Company, 1911. 12mo.; 171 pp. Price, $1.10 net. Ten days after leaving college a young Harvard man became a laborer in a non-union coal-mine of the Middle Wfst-startlng vcry literally at the bottom with the aim of leal'n- ing the business thoroughly. The ordinary work and lifc of the underground city would alone make good reading at the hands of an educated man with a sympathetic knowledge of nature values, but Husband was fortunate enough-or it is our good fortune, if you so prefer it-to experience in that one short year all the thrills that strikes, fires, and explosions are capable of furnishing. The result is a document of some value as a study of mining conditions, and of popular interest in so far as hazardous moments and adv('ntur6us days can make it. Unsoundness OF Mind. By T. S. Clous-ton, M.D., L.L.D., F.R.S.E. New York: E. P. Dutton&Co., 1911. 8vo.; 360 pp.; 14 illustrations. Pric2, $2.50 net. Popular interest las 01 late years been quickened toward this important subject. Criminals are more and more availing tbemselves of the plea of insanity in an attempt to escape punishment. We still ridicule the weak-minded and subject the Inmates Of our insane asylums to unnecessary cruelties; but we are slowly learning that a diseased brain is as much a physiological fact as a diseased liver, and that no odium should attach to its victim. Dr. Clouston handles a most difficult subject in a manner nothing short of masterly. The volume answers, or at least discusses illuminatingly, the most absorbing questions. Since a sane man oftell appears to act irrationally, and an Insane subject frequently presents no irrational thoughts or actions to our view, how may we distinguish between a sound and an unsound mind? If, in infancy, a limb is amputated, the corresponding nerve cells of the motor centers in the brain shrivel up. To what extent have we localized in the brain these various functionings? What proportion of us is really unsound in mind? Are we all a little affected, as the wen-known remark of the old Quakeress would lead us to mistrust, or is our universal mind built upon a firm foundation? Dr. Clouston sketches for us eleven orders of brain in their characteristic workings. His conclusions are optimistic, his opposing facts well weighed. The relation of heredity, of nerve exhaustion, of other causes, to unsoundness of mind and insanity, is made wonderfully clear and, not stopping at a mere presentment of the evil, suggestions for preventive and curative regimes are given. 'l'he hopeless cases are differentiated from the hopeful, mania from melancholy, the !unctional difficulties from the organic, and the workings of the brain are bared to the gaze In a way that all can understand. The volume embodies the latest theories and Olscoveries, and clearly conveys knowledge that no parent, at least, should be without. Its suggestions, if followed, would vastly decrease the world's troubles and result in the improvement of the human race. Elementary ChemistRy foR Coal-Mining Students. By L. T. O'Shea. New York: Longmans, Green&Co., 1911. 8vo.; 319 pp.; illustrated. Price, $1.80 net. As the name indicates, this book sets forth such simple chemical principles as bear upon the work, the welfare, and the safety of coal miners and the value of their product. The gases found in the air of coal mines can be adequately dealt with only by utilizing a knowledge of chemical action and combination. This touches the problem on Its life-saving and property-conserving sides. On the purely economical side of the question, coal itself must be regarded as a combination of carbon, hydrogen, nitrogen, oxygen, etc., and the proportions of these determine Its value for particular purposes. Here again chemical analysioSi is taking a part of growing importance, in that it determines the value of a coal in its application to special uses. Colliery explosions are made the subject of careful study. The book should be cordially received by all who are interested in what it has to offer. Abroad with the Fletchers. By Jane Felton Sampson. Boston: L. C. Page&company, 1911. 8vo.; 368 pp.; illustrated. Price, $1.60 net. “Abroad” has reference to the stereotyped zig-zag from Naples to Rome, Florence, Venice and Milan, through Switzerland and Western Germany, with a dash up into the Netherlands and a descent through Belgium to Paris, thence to London, to Scotland, and back to Liverpool to take the home-going steamer. “The Fletchers” are a iuaint old couple of the rural type, through whose eyes all the old familiar sights are seen from a rew angle. The sayings of Thomas Jeremiah Fletcher form no small part of the recital, which, showing a 'prentice hand, still atones by a certain freshness and spontaneity for any technical shortcomings. The illustrations are from photographs by the author, and are very clear and good. Half Hours with the Summer Stars. By Mary Proctor. Chicago: A. C. Mc-Clurg&Co., 1911. 232 pp.; illustrated. In this little book Miss Proctor has given just the kind of Information which the average astronomically-uninformed man desires about the stars. Not only does she give the mythological significance of the more important constellations of stars, bnt the result of much modern se('ntlfc discovery.